Passkey diagnostics guardrail

[pathoam]

This changeset verifies that the current environment can support basic functionality required to use the app properly and prevents users from creating an account on non-functional devices. In order to trigger the check, there is an env variable that can be set to always check, check high risk, or never. The high risk heuristic is based on devices that ship or previously did without robust built in passkey support, including chinese oems as well as the presence of google services on android and browser based check for passkey support on web. If the heuristic is triggered, or if the env var is set to always, it forces the user to immediately sign a dummy message with the new passkey to validate that it works before they can continue to the main app.

• add passkeyDiagnostic helper (packages/app/utils/passkeyDiagnostic.ts) plus tests/docs. It caches Google Mobile Services availability on native, probes UVPAA on web, and normalizes error
  messaging/toasts.
• update shared utilities: useCreateSendAccount caches the initial passkey credential and exposes diagnostic callbacks; useUser uses .maybeSingle() to stop 406 spam; fix checkbox prop
  destructuring.
• wire the diagnostic flow into onboarding and sign-up screens with identical UX—status indicator, single toast, bright retry button, and suppression of “User clicked reject” overlays.

[youngkidwarrior]

This looks good. A couple of NITs, but overall solid. Add those details about the risky vendors then go ahead and merge. Fix the NITs if you feel like it. Might save some headaches in the future

[youngkidwarrior]

• priority search for verified accounts #2035
• send token balance profile and batch functions #2034
• Upgrade supabase to v2.48.3 #2050
• Passkey diagnostics guardrail #2042 👈 (View in Graphite)
• dev

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[youngkidwarrior]

forgot. please update to use the expo devices package

[github-actions]

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